The present invention relates to novel 10-phenyl-1,3,9-triazaanthracenes and to a photopolymerizable mixture which contains, as the essential components,
(a) a polymeric binder PA1 (b) a polymerizable compound having at least two terminal, ethylenically unsaturated groups and a boiling point of more than 100.degree. C., and PA1 (c) a 10-phenyl-1,3,9-triazaanthracene as the photoinitiator. PA1 (a) a polymeric binder PA1 (b) a polymerizable compound having at least two terminal, ethylenically unsaturated groups and a boiling point of more than 100.degree. C., and PA1 (c) a polynuclear N-heterocyclic compound as photoinitiator. PA1 R.sup.4 is a hydrogen or halogen atom, an alkyl, alkoxy, halogenoalkyl, alkylcarbonyl, alkoxycarbonyl or dialkylamino group or a condensed aromatic radical, and PA1 R.sup.5 and R.sup.6 are identical or different and each denotes hydroxy, alkoxy or dialkylamino groups. PA1 R.sup.4 is a hydrogen or halogen atom, an alkyl, alkoxy, halogenoalkyl, alkylcarbonyl, alkoxycarbonyl or dialkylamino group or a condensed aromatic radical, and PA1 R.sup.5 and R.sup.6 are identical or different and each denotes hydroxy, alkoxy or dialkylamino groups. PA1 inhibitors to prevent thermal polymerization of the monomers, PA1 hydrogen donors, PA1 substances regulating the sensitomeric PA1 properties of layers of this type, PA1 dyes, PA1 colored and uncolored pigments, PA1 color formers, PA1 indicators, PA1 plasticizers, etc.
Photopolymerizable mixtures which contain the components (a) and (b) and a polynuclear heterocyclic compound as the photoinitator are known.
In German Pat. No. 20 27 467 (equivalent to British patent specification No. 1,354,541), specific derivatives of acridine and phenazine are described as initiators.
German Pat. No. 20 39 861 (equivalent to U.S. Pat. No. 3,765,898) discloses similar mixtures containing quinoxaline derivatives or quinazoline derivatives as initiators.
All these compounds act as excellent initiators when they are irradiated with actinic light, particularly from light sources emitting in the near ultraviolet range. But in recent times, metal halide-doped gas discharge lamps have become more and more commonly used for copying purposes because of their high luminous efficiency. Since these lamps have stronger emission values in the border range of the visible light, i.e., at about 400 nm and higher, than the hitherto conventionally used light sources, such as, for example, mercury vapor lamps, the absorption values of the known, highly efficient initiators are no longer optimally matched to the emissions of these light sources. Moreover, the variations possible by substitution of the known heterocyclic initiators are limited, i.e., by means of known production processes it is possible to modify other properties, such as solubility in aqueous or organic solvents or compatibility with various photopolymerizable mixtures, to only a limited degree by a purposeful synthesis.